It depends on what you're going for...if you want to superdetail pick up the "Achtung Panzer" line of books, excellent drawings and walkaround photos...If you just want a brief summary on history and a lot of pic's, IMO you can't beat Squadron books value-wise. Some of the New Vanguard books are excellent, but not as many pics.
As far as these "bibles" are concerned, I picked up the $45 Jentz Panther book. While it is an excellent book, which covers just about everything you need to know operationally about the panther and had scale drawings. I was a little disappointed in the lack of close-ups or drawings of the little details. Also I felt it was a little lacking when it came to pictures.
I guess I'm more into visual references and not as much into the words... at least as far as building the actual model.